Insulating shutter mechanism for bus bars

ABSTRACT

A control center characterized by an upright cabinet in which a plurality of vertical bus bars are disposed which bus bars are encased in a pair of planar molded barriers of insulative material which are in tight surface-to-surface contact with the bus bars for extracting heat therefrom. Openings are provided in the barriers to enable access to the bus bars at spaced intervals corresponding to the spacing between contacts on circuit interrupters located within the cabinet. Shutter means for closing the openings when the circuit interrupter is withdrawn from the cabinet are provided and the shutter means comprises a level projecting into the path of travel of the circuit interrupter for moving the shutter means to an open position when the circuit interrupter is inserted into the cabinet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This invention is related to the copending applications of John R.Wilson and Jerome C. Wolski, Ser. No. 612,529, filed Sept. 11, 1976;Forrest E. Coyle, John R. Wilson, and Brij M. Bharteey, Ser. No.612,607, filed Sept. 11, 1975; John R. Wilson, Sadiq A. Shariff, andBrij M. Bharteey, Ser. No. 612,605, filed Sept. 11, 1975; John R.Wilson, Neal E. Rowe, and Brij M. Bharteey, Ser. No. 612,606, filedSept. 11, 1975; Donald D. Armstrong and John R. Wilson, Ser. No.612,525, filed Sept. 11, 1975; and Brij M. Bharteey and Neal E. Rowe,Ser. No. 612,604, filed Sept. 11, 1975.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a control center and more particularly toinsulated vertical bus bars having access openings with shutter means.

2. Description of the Prior Art

In a motor control center, the vertical bus bars distribute power tomotor controllers arranged in a vertical stack, one above the other. Thebus bars are often enclosed within insulating barriers to preventaccidental personal contact. However, the degree of safety offered bythis means is considerably reduced by the need for access openings inthe barrier at regular intervals. The openings are required in order toestablish electrical connection between the individual controllers in astack and the vertical bus bars, usually accomplished by a sliding stabconnector. With the controller in its operating mode, there is completesafety, and no possibility of contact with the bus bars. With thecontroller withdrawn from its assigned space, however, the disconnectportion of the bus bar is clearly visible through the stab opening inthe barrier, thus presenting a safety hazard. For example, reference ismade to U.S. Pat. Nos. 3,096,131, 3,113,820, 3,170,092, and 3,840,785.

Manifestly, upon the withdrawal of a controller the openings may beclosed by a suitable cover which can be placed manually. However, such aprocedure per se presents a safety hazard.

SUMMARY OF THE INVENTION

It has been found in accordance with this invention that the foregoingproblem may be overcome by providing a control center comprising anupright cabinet having a front side, a plurality of verticalhorizontally spaced bus bars in the cabinet, a barrier of electricallyinsulative material covering the bus bars, the bus bars having spacedcontact receiving openings for each bus bar so that terminal contacts ofa circuit interrupter may be inserted into the openings when a circuitinterrupter is placed in the cabinet, shutter means for closing theopenings when the circuit interrupter is withdrawn from the bus bars,said means including a lever projecting into the path of travel of thecircuit interrupter and movable by the circuit interrupter when saidinterrupter is installed to affect opening of the shutter means.

The advantage of the device of this invention is that it provides anautomatic means for closing the openings to the exposed bus bars whenthey would otherwise be exposed and thereby provide a safety hazard.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an electrical control center inaccordance with this invention;

FIG. 2A is a front elevational view of the upper half of the controlcenter with the front doors open;

FIG. 2B is a front elevational view of the lower half of the controlcenter with two of the doors open;

FIG. 3A is a side elevational view of the control center as viewed inFIG. 2A with the doors closed and with the side panel removed;

FIG. 3B is a side elevational view of the portion of the control panelshown in FIG. 2B with the doors closed and with the side panel removed;

FIG. 4 is a horizontal sectional view taken on the line IV--IV of FIG.2B and showing a circuit breaker being inserted in place;

FIG. 5 is a perspective view of an assembly of bus bars and insulativebarriers and showing support bars for the barriers in explodedpositions;

FIG. 5A is an enlarged fragmentary view of the area encircled in FIG. 5;

FIG. 6 is a fragmentary horizontal sectional view showing the assemblyof the bus bars, insulative barriers and support brackets in place;

FIG. 7 is a horizontal sectional view showing an assembly of the busbars, insulative barriers and shutters therefore;

FIG. 8 is a fragmentary horizontal view showing one stab assembly forone circuit breaker and showing the manner in which the stab is movablefor alignment with a bus bar; and

FIG. 9 is a fragmentary horizontal view of another embodiment of themanner of mounting the stab assembly of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The electric control center of this invention is generally indicated at13 in FIG. 1 and comprises a metal cabinet having a plurality ofvertically disposed compartments such as compartments 15, 17, 19, and 21which are separated by similar horizontal shelves 23, as shown in FIG.2. Each compartment 15, 17, 19, 21 includes an access door 25, 27, 29,31, respectively, which doors are provided with or without appropriateopenings 33 to accommodate portions of circuit breakers, such as handles35, 37 or indicator light panel 39 as required.

The cabinet 13 includes a rectangular steel framework consisting ofU-shaped corner posts 41 (FIG. 4), horizontal interconnectors 43, 45 atupper and lower ends and vertically spaced horizontal braces 47. Inaddition, the steel framework consists of upright posts 49, one at thefront and rear sides of the cabinet 13. A pair of support posts 51 and53 are also disposed at opposite sides of the cabinet 13 adjacent toopposite wall panels 55 and 57 as shown in FIG. 4.

In the embodiment of the invention disclosed herein, the front and rearsides of the cabinet 13 are provided with compartments similar to 15-21on the front side in which circuit interrupters 65 may be inserted fromopposite sides of vertical bus bars 59, 61, 63 which are centrallydisposed between the front and rear sides of the cabinet 13. It isunderstood, however, that the cabinet 13 is operative similarly wherethe rear side of the cabinet is not adapted for mounting of circuitinterrupter 65. Suffice it to say, as shown in FIG. 4, the front side ofthe cabinet 13 comprises the stacked compartments 15, 17, 19, 21 on theleft side of the upright post 49 and a vertically extending compartment67 between the posts 49, 41. The compartment 67 is separated from thecompartments 15-21 by a partition 69 and from the central area of thebus bars by a partition 71. Access to the compartment 67 is provided bya vertical door 73. The compartment 67 extends vertically between theupper and lower ends of the cabinet 13 and is provided for electricwires leading from the several circuit interrupters 65 disposed in thecompartments 17, 19, 21. In the embodiments of the invention havingcircuit interrupters 65 disposed at the rear wall, a verticalcompartment 75 is likewise disposed for the same purpose as thecompartment 67.

As shown more particularly in FIGS. 2A and 3A, the upper ends of the busbars 59, 61, 63 are attached to separate horizontal buses 77, 79, 81respectively by suitable fastening means such as similar pairs of bolts83. The bus bars 59, 61, 63 extend vertically and substantiallythroughout the length of the vertical cabinet 13, whereby access to oneor both sides thereof may be had by insertion of the several circuitinterrupters 65 into appropriate compartments. As shown in FIGS. 4, 6and 7, the bus bars 59, 61, 63 are preferably Z-shaped and consist ofoppositely disposed stabs or legs 87, 89 at intermediate portions 91.The electrical capacity of the bus bars 59, 61, 63 may be increased byattaching metal bar members to the bus bars such as insurface-to-surface contact with the intermediate portions of each busbar. The legs 87 extend toward the front side and the stabs 89 extendtoward the rear side of the cabinet 13, while the intermediate portions91 are preferably aligned and in a zone parallel to the front and rearsides of the cabinet. Accordingly, each circuit interrupter 65 isprovided with similar terminal contact connectors or clips generallyindicated at 93 which move into contact with corresponding stabs 87.Although the Z-shaped bus bars 59, 61, 63 are preferably extruded unitscomprised of an integral member such as an aluminum conductor, the busbars may also be composed of separate L-shaped members which are securedtogether such as by bolting along the intermediate portions thereof. Asshown in FIGS. 2A and 3B, each circuit interrupter 65 comprises a pairof mounting members 66 which extend from each opposite side wall andengage similar mounting tracks 68, which tracks may depend from theadjacent horizontal shelf 23, or may be separate from the shelves 23 andbe mounted on adjacent frame members such as upright posts 41 and 49.

The bus bars 59, 61, 63 are enclosed within barrier means, such as apair of barriers 95, 97, which completely enclose the bus bars. Thebarriers 95, 97 are substantially coextensive with the bus bars (FIGS. 2and 3) and enclose the bus bars substantially from the upper to thelower ends thereof. One purpose of the barriers 95, 97 is toelectrically insulate the bus bars and increase the safety factor of thecontrol center. Inasmuch as plug-in type interrupters 65 are connectedto the bus bars from the front and rear sides of the cabinet 13, thebarriers 95 and 97 are preferably of identical construction. Atvertically spaced intervals, each barrier includes three horizontallyspaced openings 99, 101, 103 through which terminal connectors 93 areinserted. As shown more particularly in FIG. 4, the barrier 95 is asubstantially planar member extending between a flange 105 on the leftand a flange 107 on the right. The several openings 99, 101, 103 areprovided in the planar surfaces and are in surface-to-surface contactwith the intermediate portion 91 of the bus bars 59, 61, 63. Inaddition, the barriers include vertically extending ribs 109 of U-shapedcross section and into which the stabs 87 project. Thus, the stabs 87are enclosed by the barriers between each pair of vertically spacedopenings 99 as shown in FIG. 5. To prevent sparkover or arcing frombridging between adjacent pairs of bus bars 59, 61, 63, the barriersinclude interfitting or interlocking means between each pair of busbars, which means comprise a vertically extending member 111 thatprojects transversely from the planar surface of one barrier 95 or 97into a U-shaped member 113 extending from the planar surface of theother of the barriers 95 and 97. The surfaces between the members 111,113 are preferably tight-fitting to eliminate any air movement betweenthe adjacent bus bars. The barriers 95, 97 are identical in constructionso that the interfitting means, including members 111, 113, as well asthe U-shaped ribs enclosing the legs 87, 89, provide a labyrinth passagebetween one side or flange 105 and the other side or flange 107 of theassembly. In that manner, the possibility of sparking or arcing due toany cause such as the presence of ionized gas is avoided. It is notedthat the labyrinth assembly of the barriers and bus bars is maintainednotwithstanding the thickness of the bus bars. For example, where higherratings are necessary, bus bars of greater thickness or gauge may beused in conjunction with the same barriers without eliminating thesafety conditions created by the interfitting members 111, 113. In otherwords, each bus bar is isolated from the others by the assembly of thebarriers 95, 97.

Associated with the foregoing is an additional safety aspect of thebarriers 95, 97, which comprises laterally extending members surroundingeach opening 99, 101, 103 to provide a hood around each exposed leg 87in the openings. For that purpose, a pair of vertical flanges 115, 117and a pair of horizontal flanges 119, 121 combine to form a protectinghood around each exposed stab or leg 87 in each opening 101. In asimilar manner, the opening 99 is enclosed within upper and lowerhorizontal flanges 119, 121, as well as vertical flanges 99, 117, andthe openings 103 are surrounded by upper and lower horizontal flanges119, 121 and the members 103, 117. Accordingly, the stabs or legs 87, 89are protected from accidental contact by the members 115, 117, 119, 121around each of the spaced openings. Moreover, the provision of a hood or"boxed-in" construction around the exposed stabs minimizes anyaccidental contact with two or more of the stabs by operating personnelor misplaced conductors such as wires.

As was set forth above, the stabs and legs 87, 89 are exposed withinopenings of limited size to facilitate connection and disconnection ofcircuit breakers having terminal connectors 93 as shown in FIG. 4. Thecabinet 13, however, is so constructed that circuit interrupters ofother types may likewise be connected to the bus bars even though thecircuit interrupter is not provided with contact members such as theterminal connectors 93. As shown in FIGS. 2A and 3A, a circuitinterrupter 123 is mounted within the cabinet in the compartment 17 on asupport bracket 125 extending between the support posts 53. Conductors127, one of which is shown in FIG. 3A, extend from the circuitinterrupter 123 to the intermediate portions 91 of the bus bars wherethey are secured in a suitable manner such as by fastening bolts, notshown. For that purpose (FIG. 5A), the barriers 95, 97 are provided withknockout portions 129 of the planar area of the barriers which areeasily removed by the provision of reduced sections 131, 133 to exposethe intermediate portion 91 of each bus bar to facilitate the attachmentof the conductor 127. In addition, the reduced wall section 133 enablesthe removal of the flange 117 where necessary to provide a largerexposure of the intermediate portion 91. The exposed area, however, isprotected by the provision of an additional flange means such as flanges135, 137 (FIG. 5).

In accordance with this invention, it is noted that (FIGS. 4 and 5) thebarriers 95, 97 are in surface-to-surface contact with the bus bars 59,61, 63, including the intermediate portions 91 and the stabs 87, 89,except for those portions of the bus bar at the openings 99, 101, 103.That is, the barriers 95, 97 are in tight surface-to-surface contactwith the bus bars with no air space therebetween. In this manner, thebarriers serve as heat sinks for conducting heat away from the bus barsto the surrounding atmosphere. The increased surface area of the busbars 95, 97, including the several flanges, ribs and the like, cooperateto transfer the generated heat to the surrounding atmosphere with goodefficiency. The advantage of the surface-to-surface contact with no airspace between the bus bars and the barriers is that the barriers carrythe heat away and have good emissivity to dispel the heat better thanthe prior methods of enclosing bus bars in "dead air". It has been foundthat where the barriers are composed of a particular electricallyinsulative material in contact with the bus bars, the bus bars operate10° C. cooler than in open air and 20° C. cooler than the bus bars whichare in trapped air, that is, air that is contained within housing thatis not properly ventilated. Thus, the barriers 95, 97 serve aselectrically insulating members between each bus bar 59, 61, 63 and asisolating members to prevent personnel from accidentally touching thebus bars, such as by a screwdriver or a wire. The barriers 95, 97consist essentially of a thermal setting resinous material selected fromthe group consisting of polyester, epoxy, phenol and mixtures thereof. Asuitable material is isophthalic maleic-glycol, polyester. To strengthenthe sheet-like members from which the barriers are molded, the materialcontains an inorganic reinforcing material such as glass fiber. Inaddition, the resin includes a filler selected from the group consistingof alumina, aluminum trihydrate, beryllium oxide, calcium carbonate,mica, silica, talc, and mixtures thereof. The sheet-like members fromwhich the barriers are molded have a minimum thickness of about 0.1 inchwhich provides a light and preferably inexpensive barrier. Asatisfactory commercial material is Rosite 3550FM, which is a trademarkof the Rostone Company of Lafayette, Indiana.

The assembly of the barriers 95, 97 and the bus bars 59, 61, 63 aremaintained in tight surface-to-surface contact as well as in positionwithin the cabinet 13 by a pair of horizontal braces 139, 141 (FIGS. 2A,3A, 4, 5, 6). The end portions of the brace 139 are secured by bolts 143to the support post 53 and (FIG. 6) the brace 141 is secured to thebrace 139 by bolts 145. Several pairs of the braces 139, 141 aredisposed at vertically spaced intervals along the length of the assemblyof the barriers and bus bars. The brace 139 includes a bar 147 and achannel member 149 secured thereto in a suitable manner, such as weldingor riveting. The channel member 149 includes horizontally spaced notches151 and 153. Likewise, the brace 141 comprises a bar 155 and a channelmember 157. The channel member 157 comprises notches 151 and 153 similarto those on the channel member 149. When in place opposite edges of thechannel members 149, 157 engage the planar surfaces of the barriers 95,97 at 159, the notches 151 surround and engage the ribs 109, and thenotches 153 surround and engage the U-shaped member 113. The braces 139,141 are retained in clamping engagement with the insulative barriers bytightening nuts 146 on the bolts 145 to maintain the barriers 95, 97 intight surface-to-surface contact with the bus bars 59, 61, 63. Theadvantage of the pair of braces 139, 141 is that the braces on each sideof the assembly hold the barriers tightly in place to maintain theintimate contact between the barriers and the buses for satisfactoryheat transfer and for maintaining isolation between the spaced bus bars.They also support and brace the bus bars against the effects ofelectromagnetic forces generated under short circuit conditions.

When one or more of the circuit interrupters 65 are removed from thecabinet 13, the stabs 87 are exposed through the openings 99, 101, 103so as to provide an unsafe condition. For that reason, shutter means areprovided for closing the several openings when a circuit interrupter 65is removed from a particular compartment 19. As shown in FIG. 2A, by wayof example, a shutter 161 is mounted on each barrier 95, 97 to cover theopenings 99, 101, 103 in each horizontal group. The shutter 161 is asheet-like member consisting of a dielectric material such as thematerial comprising the barrier 95, 97. The shutter 161 comprises threeholes 163 which are horizontally spaced by a distance corresponding tothe spacing between the openings 99, 101, 103. As shown moreparticularly in FIG. 5, up-turned and down-turned tabs 165 and 167 areprovided on the flanges 119, 121 at each opening in the barrier forretaining the shutter 161 in place. The shutter is movable horizontallyby a cam or lever 169 which is operatively connected to the shutter 161by a connecting member 171 (FIGS. 2B, 4, 7). The cam or lever 169 is arod-like member, one end portion of which is turned at substantially aright angle for connection to the shutter and the intermediate or bodyportion of which extends through an opening (not shown in FIG. 4) andthrough a mounting bracket 173 which is attached to the corner post 41.The body portion of the lever 65 includes an outwardly inclined camsegment 175 which extends into the path of travel of one side of thecircuit interrupter 65A. When the circuit interrupter 65A is moved intothe compartment 19 toward the legs 87, it contacts the cam segment 175and thereby rotates the lever 169 counterclockwise (FIG. 2B) to move theshutter 161 to the left in order to align the holes 163 with theopenings 99, 101, 103. Thus, the terminal connectors 93 are free to moveinto engagement with the corresponding stabs 87 as shown with the fullyinserted circuit interrupter 65 in the rear portion of the cabinet inFIG. 4. An end portion 177 of the lever 169 extends through a slot inthe mounting bracket 173 and is biased upwardly by a spring 179 (FIG.3B) in order to rotate the lever to the shutter-closed position when thecircuit interrupter 65A is withdrawn. The position of the lever 169 inthe shutter-open position is shown in FIG. 2B. Thus, the combination ofthe barriers 95, 97 and the shutters 161 combine to providesubstantially total enclosure of the bus bars 59, 61, 63 and therebymaximize personnel safety and equipment protection.

The electrical connection between the individual motor controller unitor circuit interrupter 65 and the vertical bus leg 87 requires afloating type of terminal connector 93 in order to effect positivecontact alignment and guiding to the bus bar stab. The terminalconnector 93 for each phase (FIG. 4) is contained within a cover orhousing 181 which is shown more particularly in FIG. 8. The terminalconnector 93 comprises a pair of oppositely disposed flexible contacts183, 185, the outer ends of which are flared outwardly at 187 forguiding the connector 93 into alignment with the stab 87. The flexiblecontacts 183, 185 are secured together such as by a weld at 189 andlower end portions 191 and 193 are flared outwardly in oppositedirections as shown. A conductor assembly 195 is secured to one of theout-turned portions 93. More particularly, the terminal connector 93 ispivotally mounted on pivot point 197 which extends into a groove 199formed by the out-turned end portions 191, 193. The connector 93 beingcontained within the housing 181 is free to rotate right or left aboutthe pivot point 197, which rotation is limited by projections 201 of thehousing 181. Thus, the out-turned end portions or flanges 191, 193,being disposed between the projections 201 and a recess wall 205 in thehousing, are limited in their degree of rotation about the pivot point197. The extent of rotation on either side of the pivot, however, iswithin reasonable limits of misalignment between the axis of theterminal connectors 93 and a particular legs 87 so that when the circuitinterrupter 65A is moved into engagement with the legs 87, the contacts183, 185 rotate into proper alignment. Inasmuch as the housing 181 is ashell-like member surrounding and mounting the terminal connectors 93 inplace, it is provided with an opening 207 through which the conductor195 passes into the main portion of the circuit interrupter 65. Anotherembodiment of the means for mounting the terminal connector 93 is shownin FIG. 9 in which similar numbers refer to similar parts of FIG. 8. Apivot point 209 may be provided as a part of the contacts 183, 185,which is located within a pivot notch 211 in the housing 181. In asimilar manner, the terminal connector 93 is free to rotate to a limitedextent in either embodiment of FIGS. 8 and 9 as limited by theprojections 201 and the recess wall 205.

Accordingly, the motor control center of this invention provides newconcepts in metal enclosed control units to enable the increase range ofuseful operation. By providing safeguards for both personnel andequipment, the motor control unit of this invention is readily adaptableto a variety of operating conditions including circuuit interrupters ofvarious types without sacrificing safety.

What is claimed is:
 1. A control center for distributing electric powerfrom a power supply source to power-consuming devices, comprising acabinet having a frame providing a compartment on the front side of thecabinet, a plurality of vertical, horizontally spaced, bus bars in saidcabinet, a barrier of electrically insulative material covering the busbars, the barrier having spaced contact-receiving openings for each busbar so that terminal contacts of a circuit interrupter may be insertedinto the openings when a circuit interrupter is placed in the cabinet,shutter means for closing the openings when the circuit interrupter iswithdrawn from the bus bars, said means including a planar shutterextending across the spaced openings and having spaced apertures; theplanar shutter being slidable between aligned and unaligned positions ofthe openings and apertures which positions correspond to installed andremoved positions of the circuit interrupter, shutter-opening meanscomprising an elongated rod rotatable about its axis and having anoutturned portion operatively connected to said shutter, and theshutter-opening means also comprising an outwardly inclined cam segmentextending into the path of travel of the circuit interrupter so that therod is rotated to move the shutter to the aligned position when thecircuit interrupter is installed.
 2. The control center of claim 1 inwhich the shutter means is biased to the closed position.
 3. The controlcenter of claim 1 in which the rod is rotatably mounted on the frame.